PM / runtime: add note about re-calling in during device probe()
The sh_eth driver has come up with an issue where the runtime_pm
code suspends it during the probe() method due to the network
device registration re-calling into the driver.
Add a note about this into the documentation.
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index 44fe1d2..e76dc0a 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -556,6 +556,12 @@
should be used. Of course, for this purpose the device's runtime PM has to be
enabled earlier by calling pm_runtime_enable().
+Note, if the device may execute pm_runtime calls during the probe (such as
+if it is registers with a subsystem that may call back in) then the
+pm_runtime_get_sync() call paired with a pm_runtime_put() call will be
+appropriate to ensure that the device is not put back to sleep during the
+probe. This can happen with systems such as the network device layer.
+
It may be desirable to suspend the device once ->probe() has finished.
Therefore the driver core uses the asyncronous pm_request_idle() to submit a
request to execute the subsystem-level idle callback for the device at that